Reference

ChanYeung M, Lam S, Koener S, Clinical features and natural history of occupational asthma due to western red Cedar (Thuja plicata), Am J Med, 1982;72:411-415,

BOHRF Original Authors' Main Conclusions

The original authors' main conclusions are taken from Abstract, Results and Discussion. They are decided upon by the authors of the BOHRF occupational asthma guidelines and form part of the guidelines.

50/125 subjects remained in the same job and all had respiratory symptoms. In 75 exposures ceased. Of these, half became asymptomatic. Noted that subjects who became asymptomatic had relatively normal lung function at time of diagnosis. Asthma was often not recognised; it took an average of 2 years after onset of symptoms to reach correct diagnosis. Subjects with shorter duration of exposure and shorter duration of symptoms prior to diagnosis and removal from exposure showed improvement. Early diagnosis and removal from exposure were found to be associated with recovery.

BOHRF Associated Evidence Statements

The BOHRF occupational asthma guidelines state that this reference is associated with the following evidence statements

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2+

The symptoms and functional impairment of occupational asthma caused by various agents may persist for many years after avoidance of further exposure to the causative agent.

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2++

The likelihood of improvement or resolution of symptoms or of preventing deterioration is greater in workers who have no further exposure to the causative agent.

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2+

The likelihood of improvement or resolution of symptoms or of preventing deterioration is greater in workers who have relatively normal lung function at the time of diagnosis.

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2+

The likelihood of improvement or resolution of symptoms or of preventing deterioration is greater in workers who have shorter duration of symptoms prior to diagnosis.